Solids Flashcards
Two types of solids
Crystalline, amorphous
Solids with a highly regular arrangement of their components. Ex. Diamond, quartz, NaCl
Crystalline solids
Solids with considerable disorder in structures. Ex. Plastic, glass, rubber
Amorphous
Atoms, ions, or molecules packed in regular geometric arrays are called
Lattice
Smallest repeating unit of a lattice
Unit cell
Number of nearest neighbor atoms in a lattice
Coordination number
Recall summary of unit cells
Recall contribution of atoms on each part of a unit cell
Formed when a group MO energy levels with closely spaced energies
Band
Valence band: highest energy band
Conduction band: partially filled or empty band where electrons can move
Metals are good conductors in lower temp
Semiconductors (mettaloids) are good conductors in higher temp
In insulators there is a _____ band gap between valence and conduction bands that prevents the motion of electrons
Large
Addition of impurities
Doping
Semiconductors whose electrical properties are enhanced by doping
Extrinsic semiconductors
____ have small band gap between valence and conduction bands
Semiconductors
Elements that exhibit semi-conductive behavior at their pure state are called ____, including Se, Ge, and alpha- Sb
Intrinsic semiconductors
The conductivity of intrinsic semiconductors are further enhanced by doping semiconductors with other elements using ____ and ____
N-type and P-type dopants
N-type dopants (G15) are capable of doping intrinsic semiconductors because because of their additional _____ relative to the host semiconductor.
Free electron.
Note. > valence electron than the element in focus
P-type dopants (G13) provide positive ___for increaing the conductance of semiconductors.
Holes
Note. < valence electron than the element in focus
Mixture of metals and another element
Alloy
An alloy wherein some of the host metal atoms are replaced by other metal atoms of similar size
Substitutional alloys
An alloy that is formed when some of the interstices or holes in the closest packed metal structure are occupied by small atoms
Interstitial alloy
Presence of the interstitial atoms changes the proprties of the host metal
Steel is an example of interstitial alloy
Solids that are characterized by strong covalent bonding within molecules (IMFA) but relatively weak forces between molecules
Molecular solids. They are relatively soft snd have the lowest melting point
Solids that are held together by covalent bonds , and have atoms occupying ghe lattice points
Network Covalent or Atomic Solids. They have the highest melting point and they’re made up of nonmetals
Solids that are high melting substances held together by strong electrostatic forces that exist between oppositely charged ions
Ionic solids
The structures of most binary ionic solids can be explained by closest packing of spheres. Large anions are packed by either FCC or HCP, while smaller cations fit into holes among the closed packed anions.
Packing is done by maximizing the repulsions amon ions with similar charges.
Three types of holes in closest packed structures
Trigonal, tetrahedral, octahedral ions
The stronger the bond that holds the solids together the higher the melting point
The smaller size of ion with higher charge the greater the lattice energy
___ refers to the change in energy that takes place when separated gaseous ions are packed together to form an ionic solids
Lattic energy
The process of considering the component reactions that can be imagined as the individual steps in compound formation
Born-Haber Cycle
Reflects the effect of geometry of lattice on the strength of net coloumbic interaction
Madelung constant
Recall 7 crystal system
Triclinic
Monoclinic
Orthorhombic
Rhombohedral
Tetragonal
Hexagonal
Cubic
CCP- 3 repeating layers
HCP- 2 repeating layers
Conduct current at one direction, using pn junction as basis.
Diode. Used as rectifiers, voltage regulators, and modulators
Formed when semiconductor is exposed to light generating electron-hole pairs, increasing conductivity
Photodiode
Allows current to be controlled by a small change in potential difference
Transistors. Used in amplifiers
Solubility of salts in water. In general, the difference in size favors solubility in water. The interaction responsible for lattice enthalpy are replaced with hydration enthalpy.
If cation has larger hydration enthalpy than it’s anion partner or vice versa, then the dissolution of salt is exothermic
Imperfections of structure or composition contained by all solids
Defects
Defects that occur in pure substances
Intrinsic
Defects that stems from the presence of impurities
Extrinsic
Defects that occur at single site
Point defect
Defects that occurred in 1, 2 and 3 dimensional. Also gives colors to the gemstones we have.
Extended defects
